The present invention relates to a device for drying a running web, for example, the drying section of a paper manufacturing machine. A drying section is disclosed in DE 43 28 554 A1 and is divided into a plurality of successive cylinder groups. Each of these cylinder groups comprises, as a rule, a plurality of heatable drying cylinders which come into contact with the web and which are coupled, for example, via gearwheels and/or an endless supporting belt ("felt"), to a common drive which determines the operating speed of the cylinder group.
The above German patent document DE 43 28 554 A1 discloses that, as also in the subject matter of the present invention, in the initial region of a drying section, preferably a plurality of single-felt cylinder groups are provided, which can be of quite different design. In the end region of the drying section, on the other hand, at least one two-felt cylinder group is provided. For the most part, two (or three) of this type of two-felt cylinder groups are preferred, of which each has an upper and a lower row of cylinders, the web running alternately over the upper and the lower cylinders. From cylinder to cylinder, a free, unsupported web path is provided. Each two-felt cylinder group has in turn a drive of its own. The term "felt" also includes the porous (endless) drying fabrics mostly customary today.
The present invention is concerned with the problem of the threading of the paper web into a paper manufacturing or paper processing machine (for example at start-up of the machine or after an unintentional break of the paper web). This threading of the paper web is carried out mostly, as is known, at full operating speed. When, during threading, the paper web has reached a determined position, for example, the end of the drying section, it is first led, as is known, as broke down into a broke pulping system. At the same time, at one of the two web edges, an initially narrow web part ("edge strip") is severed from the web by means of a tail-cutter. Initially, only said edge strip is transferred to the following units (for example, calendar and winder or coating units). The tail-cutter then runs to the other web edge, so that the transferred web part finally has the full web width. Normally, the tail-cutter is arranged in the end region of the two-felt cylinder group or of the last two-felt cylinder group; see FIG. 1, 12 or 13 of the above-referred to DE '554.
The above-described method is practiced in numerous paper machines, mostly with good success, even in manufacturing machines with relatively high operating speeds. However, it is desirable to be able to carry out the transfer of the paper web from the drying section into the following units with even greater reliability than previously. In this case, it is to be taken into account that, in many cases, the operating speed is intended to be increased even further, approximately to the order of magnitude of from 1600 to 2400 m/min. In so doing, the risk that the paper web breaks during tail-cutting is increased. In such an event, an additional difficulty is that the large quantities of broke accumulating in a short time do not always reliably automatically reach down into the broke pulping system, but instead scraps of broke from time to time remain unchecked in the drying section.